Electric-arc lamp for search-lights, projectors, and the like.



H. BECK. ELECTRIC ARC LAMP FOR SEARCH LIGHTS, PROJECTORS, AND

APPLIOATION FILED DEC. 12, 1911.

1,029,787, 7 Patented June 18, 1912.

I chwmtaz: y

highly loaded carbons,

HEINRICH BECK, OF lMEININGEN, GERMANY.

ELECTRIC-ARC LAMP FQR SEARCH-LIGHTS, PROJECTQRS, AND THE LIKE.

Specification of Letters Patent.

Patented June 18, 1912.

Application filed December 12, 1911. Serial No. 665,328.

To all whom it may concern:

' Be it known that I, HEINRICH BEoK, a subject of the German Emperor, and residing at Meiningen, Germany, have invented certain new and useful Improvements in Electric-Arc Lamps for Search-Lights, Projectors, and theLike, of which the following is a specification.

My invention relates to methods of working electric arc-lamps and to arrangements of electrodes for search-lights, projectors and the like.

' A primary object of my invention is to improve the output of light of electric arclamps for searchlights, projectors and the like by' forming an intensely luminous positive crater which is as small as possible. To this end, I employ electrodes containing light-emitting admixtures, e. g. metallic salts or carbids either in the form of a core or as admixtures with the, carbon, or in the form of a metallic core of the positive electrode, and I make the diameter at the tip of the positive electrode of this kind very small as compared with the diameter of electrodes heretofore customary for like strengths of current. For example, by employing suitable means described hereinafter, the diameter at the tip of the positive electrode can be smaller than that which is normal for the largest section of the luminous crater at the tip for a predetermined strength of current when carbons without light-emitting admixtures are employed and when these means are not employed. Thin electrodes thus highly loaded with light-emitting admixtures or provided with metallic cores are protected in a suitable manner by an envelop or jacket of indifferent or reducing gases or vapors from being overheated and prematurely destroyed. In the case of thin, and particularly, when the strength of current is great, the gaseous jacket fulfils another special purpose. In these thin electrodes traversed by heavy currents the current has a great tendency at the tip of the positive carbon to go over to the shell outside the crater, so that the current does not issue, asdesired, only at the end of the carbon. Now when such highly loaded, thin electrodes are supplied in the hereinafter described manner with a jet of vapor or gas, I have found that the arc is completely displaced from the outer portion of the carbon.- Consequently, the current issues only at the crater of the electrode results.

end of the carbon,

whereby a considerable concentration on the The temperature at the end of the carbon is exceedingly-increased, the crater prevented from spreading laterally bores its way into the carbon provided with light-emitting admixtures, and the vapors filling the crater in .combination with the remainder of the white-hot carbon vapor result in a very greatly increased emission of light. The increase in the specific luminosity of the crater calculated from the diameter of the greatest cross-section of the crater as compared with ordinary carbon craters amounts in the new arrangement to 300% and may possibly be increased still more.

\Vhen a gaseous or vaporous jacket is employed around the positive carbon provided with light-emitting admixtures or with a metallic core considerably thinner carbon rods can be employed than normally corresponds with the diameter of the crater of carbons customary heretofore in search- -lights. According to Nerz the normal diameters of customary carbons is for:

20 amperes' 9 mm. 80 amperes 15.3 mm. I

40 10 mm 100 8 mm.

to c 12 1 mm 120 20 mm. 70 13 5 mm 150 23 mm.. etc.

Now if, for example, according to the above table, the crater of a. 120 ampere lamp were 20 mm. in diameter in the customary arrangement and employing customary carbons, according to my new arrangementsuch a lamp can be worked with carbons 13 mm. in diameter. The crater cannot be larger than 13 mm. in diameter. Owing to this diminution in diameter of the crater the so-called' strengthening capacity of the reflector of the search-light is increased which behaves as D zal when D designates the diameter of the reflector and (Z the diameter of the crater. The gaseous or vaporous envelop or jacket may be produced either directly in the lamp, or a suitable current of gas or vapor may be supplied to the electrode. Coal-gas, carbonic acid gas, nitrogen, hydrogen, acetylene as well as vapors ofbenzin, ether, alcohol and the like may, for example, be employed. The causes of the action of such a gaseous or vaporous jacket, particularly the causes of the are being limitedto the end ofthe carbon are as yet not completely explained theoretically. It is probable that the current of gas or vapor cools the carbon shell and consegaseous or vaporous jacket may also cooperate. because, for example, at the parts of the s hellof the carbon around which the current of vapor or gas flows the surface is coated with a layer of graphite when gases or vapors contalnmg carbon, 6. q. hydrocarbons, are used.- Also, mechanical influences of the .flowmg current of gas 'may play a part. It isprobable that all the mentioned influences and perhaps others which are unknown when operating together bring about the total effect.

The gaseous or vaporous jacket may be supplied to the carbon through a suitably connected nozzle. A vaporous or gaseous jacket can also be formed by liquids, which can be gasified or vaporized, or solid substances being converted near the electrode into the form of vapor or gas and by the jet'of vapor or gas thus formed-being conducted onto the positive electrode. Further, for producing the vapor or gas the heat of the arc can be utilized. The vaporable substances can' also be preliminarily'heated or vaporized by means of a separate source of heat, 6. g. an electrical resistance.

The carbons may be provided with. ribs or grooves, e. g. be made of stellar section, whereby, on the one hand, the cooling surface for the vaporous or gaseous jacket is increased and, on the other hand, whenthe diameter of the carbon at the rear end is large the diameter of the crater end of the carbon can be diminished corresponding to the height of the ribs which burn away more readily. I

It has been found preferable for obtaining steady burning slowly to rotate the positive carbon while it burns, in order to remove the deposit of soot produced on the carbon when combustible gases are emplo'yed.

The combustible vapors or gases constituting the jacket which surrounds the carbon and is finally burned can be neglected as regards their luminosity in comparison .with the quantity of light emitted by the crater.

As negative electrode either an ordinary carbon can be employed or, however, a car-.

bon of specially small diameter surrounded, like the positive electrode, with a gaseous acket. This is of special importance for obtaining a positive crater which burns as quietly as possible when working searchlights with heavy currents and highly load- When heavy currents are employed the negative electrodes of small diameter burn away rela tively rapidly, because the negative elec-.

trdde generally has,. .a. greater length made red hot. When gases or va ors which im pede the rapid combustion o the thin negative carbon are also supplied according to my invention to the burning end of the thin negative elect-rode, a gaseous jacket or envelop very poor in oxygen is formed around the negative carbon. As the gases or vapors employed in this case are partially good conductors of heat, owing to the supply of gas or vapor to the negativeelectrode this electrode is also cooled in a desirable manner and the consumptionv and heating of the negative carbon are impeded still further. In view of the high current density of the thin negative electrode I preferably employ a carbon having a metallic coating which can be made electrolytically, or a carbon having a metallic core. The surface of the negative carbon may be artificially increased by ribs or grooves in order that the cooling action of the gases may have as large a surface as possible on which to act, and also in order that as slender a tip as possible may be formed on the negative electrode. It has also proved particularly suitable to provide the negative electrode with a core of a material more refractory than that of which the shell of the carbon is composed. A vaporous or gaseous jacket can be formed at the negative electrode as in the case of the positive electrode by converting liquids or solid substances near the negative electrodes or by means ofa separate source of heat into the form of vapor or gas and conducting the jet of vapor or gas thus formed to the negative electrode. The feed mechanism of the lamp ispreferably so constructed that the negative carbon is fedmore rapidly than the positive, 6. g. at twice the speed.

Some illustrative embodiments of my invention. and arrangements. of electrodes suitable for carrying my method into practice are represented diagrammatically by way of example in the accompanying drawing, wherein Figure 1 shows one arrangement of electrodes, a positive electrode being surrounded by a gaseous jacket, and Fig. 2 shows another arrangement of electrodes, the negative electrode being-located in a stream of gas; Figs. 3 and 4 show modifications of the arrangement shown in Fig. 1, and Flg. 5 diagrammatically represents the general arrangement in a search-light.

Referring firstly to Fig. 1, an arrange ment of the electrodes according to my invention is here shown, in which only /the positive electrode a is surrounded by a g asenegative electrode 9 of stellar cross-section,

as shown, as directed upon it a current of gas 2' issuing from a nozzle of suitable shape. The electrodes 9 may have a core 71 of any suitable material that is more refractory than the carbon shell around the core. A point Z is formed at the tip of the nega tive electrode 9. When a combustible gas e. g. coal-gas, is employed, the gas will ignite and surround the electrode 9 in the form of a flame.

Fig. 3 shows an arrangement ofelectrodes similar to that in Fig. l, but the negative electrode g is also surrounded by the jet of gas or vapor which issues from the posi- 'tive electrode a and in this case is preferably supplied at a higher pressure to the nozzle fFthan is the gas supplied to the nozzle 'of Fig. 4: shows another modification of the arrangement according to Fig. 1 in which the metallic tube 0 surrounding the positive carbon has in it a cylindrical chamber (Z which opens toward the end of the positive electrode through a number of fine nozzlelike holes (Z Fig. 5 shows in section in a search-light one form of the general arrangement when liquids are employed for forming a vaporous jacket. The positive electrode a has one or more longitudinal ribs a and is led into a thick metallic tube b which may be provided with cooling ribs 6 The current of vapor is supplied to the chamber d in the tube 6 through the pipe or nozzle f which-is fed by way of the tube 0 from the receptacle an. attached to the rear wall of the searchlight. The supply of the liquid can be regulated by a screw p and it is vaporized either by the heat which is generated in the casing of the search-light, or its vaporization can be brought about or aided by a special heating device outside the search-light casing, c. 9., as indicated, by an electrical resistance In the illustrative embodiment the current is supplied to the positive electrode by means of contact pins 1 which are arranged in the tube 1) and are pressed by a plate t under the pressure of acoil spring .9. The positive carbon a is led outward preferably through the front part of the search-light, e. g. the glass and the screen, and rotated for preventing. the deposit of soot and for obtaining uniform burning. When gas is supplied directly, the gas tube will be directly connected to the pipe or nozzle f The above-described arrangements according to my invention may be modified in very various ways as will be readily understood from the foregoing.

I claim 1. The herein described method of worl ing electric arc-lamps for search-lights or projectors comprising a positive and a negative electrode, the positive electrode containing light-emitting admixtures of metal,

metallic salts or carbids, which consists in subjecting the positive electrode to the influence of a jet of an indifferent gas or vapor during the Working of the lamp, for the purpose specified.

2. The herein described method of working electric arc-lamps for search-lights or projectors comprising a positive and a negative electrode, the positive electrode containing light-emitting admixtures of metal, metallic salts or carbids, which consists in subjecting both the electrodes to the influence of a jet of an indifferent vapor or gas, for the purpose specified.

3. In an electric arc-lamp, the combination of a positive electrode, a negative electrode, the positive electrode containing light-emitting admixtures of metal, metallic salts or carbids, and having a diameter smaller than the diameter of the crater for the same current in an arc-lamp comprising a positive electrode without a light-emitting admixture, means for concentrating the current density at the end of the crater of the positive electrode and for limiting the oxidation of the remainder of the end of the positive electrode, and means for supplying an electric current to the electrodes, substantially as described, for the purpose specified.

4. In an electric arc-lamp, the combination of a positive electrode, a negative electrode, the positive electrode containing light-emitting admixtures of metal, metallic salts or carbids, and having a diameter smaller than the diameter of the crater for the same current in an arc-lamp comprising a positive electrode without a light-emitting admixture, anozzle near the tip of the positive electrode for supplying a jet ofan indifferent gas or vapor to the positive electrode, and means for supplying an electric current to the electrodes, substantially as described, for the purpose specified.

5. In an electric arc-lamp, the combination of a positive electrode, a negative electrode, the positive electrode containing light-emitting admixtures of metal, metallic salts or carbids, a metallic tube surrounding the positive electrode for supplying an electric current thereto, said tube having a cavity at the front end thereof, a nozzle opening into said cavity for supplying an indifferent gas or vapor to the ositive electrodes, substantially as descrlbed, for the purpose specified.

6. In an electric arc-lamp, the combination of a positive electrode, a thin, negative electrode, the positive electrodes containing light-emitting admixtures of metal, metallic salts or carbids, means for surrounding the tip of the positive and of the negative electrode with a jacket envelop of an indifierent gas or vapor during the working of the lamp, and means for supplying an electric current to the electrodes, "substantially as '10 described,'for the purpose specified.

The foregoing specification signed at C0- burg, Germany, this 29th day of November,

S. HINzE. 

